Characterization of Silicone Rubber Degradation Under Salt-Fog Environment With AC Test Voltage

In recent years, some composite insulators operating in coastal foggy areas have shown different levels of degradation phenomena. This paper presents several performances and properties of silicone rubber under the salt-fog environment with AC voltage. Analysis conducted after salt-fog treatment by techniques, such as static contact angle, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), dielectric parameter, and flashover voltage show a significant degradation of samples. The absorption peak of the hydrophobic groups (Si-(CH3)2 and Si-CH3) decreased, the surface of the material became rough, and the dielectric and electrical properties were also deteriorated. Due to the thermal effects and impact of high-energy particles, the molecular chains on the surface of silicone rubber were broken, and the smooth surface structure was destroyed, resulting in the formation of hydrophilic chemical bonds and precipitation of inorganic substances. The intrusion of moisture further reduces the dielectric parameters and the electrical strength of the material. In addition, the samples in the salt-fog environment with a greater conductivity are more degraded, indicating that the salt-fog has an aggravating effect on the aging of the silicone rubber. Thus, it is recommended to pay attention to the monitoring and examining the work of composite insulators operating in a foggy and high humidity environment.